The 13th Amendment to the Constitution of the United States ended most Slavery in the United States with just
one anomaly two anomalies. It was passed within a decade of the end of the American Civil War. It doesn't extend to forced labour in privately-owned prisons, and more recently doesn't apply to forced Texan pregnancies.
Neither slavery nor involuntary servitude, EXCEPT as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction. -Section I, 13th Amendment